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Biology 202
2002 Second Paper
On Serendip

Parkinson's Disease - the chances of a trembling body

Kornelia Kozovska

I have been closely following the news in the past months and I have noted a continuum in the coverage of the medical condition of one person who for many symbolizes the virtues of man, has been associated with the liberation of the minds of people under the communist era, has firmly supported the foundations of the Catholic faith and has been inspiration for many - the current Pope John Paul II. The newspaper photos of his almost expressionless face and the constant trembling hand which have started hindering his public activities and my deep respect to the his achievements made me look into the roots of the Parkinson's disease and its effects on behavior.

Parkinson's disease, or the "shaking palsy" as first defined by Dr.Parkinson in the early 19th century, is defined as a disorder of the central nervous system, affecting about 2% of the world's population. It is more common among older people and there is a higher percentage of men affected by it. (1)Cells in the part of the brain that control movement are lost, causing sometimes severe difficulty in performing movements with a variable intensity depending on the individual cases(2) The widely recognized symptoms include muscular rigidity, resting tremors, bradykinesia, inconsistency of posture, dementia. All of these symptoms directly or indirectly affect the patient's behavior. The symptoms only appear after the death of 80% of the cells which produce dopamine. (4) The loss of dopamine causes the nerve cells of the basal ganglia to fire out of control, leaving patients unable to direct or control their movements in a normal manner. Thus, the early diagnosis is very hard, especially in the sporadic cases. Early symptoms of the disease include a drop in energy or a loss of coordination, impaired handwriting, reduced arm swing, a tremor on one side of the body, soft voice, depression. (7)

The explanation of the processes in the nervous system, which lead to the distressing results of a completely changed lifestyle as well as behavior, is important for understanding the origins of the disease. For all movements/actions the body performs, the brain gathers information about the body position which comes together in the striatum. The striatum, in cooperation with the substantia nigra and other parts of the brain, sends out commands for balance and coordination. The substantia nigra produces dopamine, the neurotransmitter which is crucial to human movement and controlling of balance. In Parkinson's disease, there is a dying off of the nerve cells producing dopamine in the substantia nigra, resulting in a large loss of dopamine in the brain, which causes a disbalance in the dopamine/acetylcholine cooperation. (6)The effects are a lack of coordination of movements, manifesting through tremor, stiff muscles, difficult moving.

There appear to be two categories of the disease - the sporadic form which does not seem to be inherited and the non-sporadic or the familial form. For a long time the wide spread hypothesis had been that the causes were almost exclusively due to environmental factors, even though in many cases the exact environmental factor has not been pinpointed. However, in 1996 there was a breakthrough discovery which suggested that a genetic alteration is capable of causing the disease. (5)A gene mutation on a gene, called alpha-sunuclein, found on the so-called long arm of chromosome 4, was identified by studying a large Italian family which had a relatively high number of Parkinson's disease cases. (6)However, the symptoms of familial Parkinson's are identical to those in families with no history of the disease, except that sometimes the disease may develop earlier in life. (5) Additionally, the sporadic-form patients did not have the gene mutation. This demonstrated the fact that at least two types of Parkinson's disease, with and without mutation, exist at the molecular level. (6)

In terms of treatment, the most widespread way has been through medications, mainly concentrated on increasing the level of dopamine or mimicking the role of dopamine in the brain. As of this moment, there has been not found a way to stop the loss of dopamine. All cures have extended their function to slowing down the decline of the loss or of the function of the neurotransmitter. There is also the Pacemaker which is a wire surgically implanted within the brain, similar to the cardiac pacemaker. Patients can activate manually the device in the occurrences of tremors. The more drastic treatment involves surgical intervention whose long-term effects are, however, still questionable. The newest research advancements have shown that implanting pig embryonic cells, which are similar to human dopamine cells, into the brains of people with Parkinson's may help improve symptoms. (8)

While doing my research on the topic, I encountered numerous websites for consultation, discussion groups, chapters and support networks for people suffering from Parkinson's. While reading some of the testimonies of those people, I was shocked by the extent to which the disease has influenced their lifestyle, their relationships, and more generally their behavior. (9) Patients talk about the inability to relate to people, the incredible difficulty in keeping their old life, the motivation, the pursuing of personal interests. There is, apparently, a very drastic change in behavior, both in terms of the visible syndromes as well as the attitudes of the patients. This could very well serve as a clue towards our discussion of the relationship between brain and behavior. How can we account for such drastic alternations in people's behavior and disregard the direct dependency on processes in the brain?


1) Parkinson's disease: An Overview
2) Parkinson's Disease Society.
3) Parkinson's Information.
4) BBC Health News. , BBC News Agency with certain articles on current research
5) Research News.
6) Molecules of the Mind: Dreaming of Parkinson's. , interesting article
7) The Parkinson's Institute
8) An Active Web Resource for Parkinson's Disease Information
9) An Online Support Group for Patients

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